First-Trimester Cardiac Myxoma Diagnosed at 12 Weeks with Postmortem Validation.

Primary cardiac tumors are extremely rare in fetal life, with rhabdomyomas being the most frequently encountered. In contrast, fetal cardiac myxomas are exceptionally uncommon, and reports of diagnosis during the first trimester are exceedingly rare. We report a fetal right atrial myxoma diagnosed at 12 weeks' gestation. Fetal echocardiography revealed a hyperechoic, pedunculated mass originating from the right atrial wall. Serial follow-up demonstrated rapid tumor growth, with increasing pericardial effusion and reversed A-wave flow in the ductus venosus by 14 weeks' gestation, indicating early and severe hemodynamic compromise. After detailed parental counseling regarding the poor prognosis, the pregnancy was electively terminated. Postmortem examination revealed a gelatinous intracardiac mass, and histopathological analysis confirmed the diagnosis of cardiac myxoma, showing stellate cells embedded in a myxoid stroma. To our knowledge, this represents the earliest gestational age at which a fetal cardiac myxoma has been diagnosed and histopathologically confirmed. This case highlights that fetal cardiac myxomas, although histologically benign, may demonstrate rapid progression and lead to significant hemodynamic deterioration even in the first trimester, underscoring the importance of early fetal echocardiographic evaluation and timely parental counseling.